Method and apparatus for improved detection of holes in plastic containers

Abstract

A method and apparatus for monitoring the production of blow molded plastic containers is disclosed, wherein the method and apparatus utilize a sound detector assembly adapted to be positioned adjacent a mold cavity during the introduction of pressure fluid to a preform in the mold cavity to form a container, the sound detector assembly including a reflector having a substantially conic cross-sectional shape and a sound detector and being responsive to a defect sound of the pressure fluid escaping from the interior of the container for generating an output signal.

1 . A method for monitoring the production of blow molded plastic containers to detect a defect in any of the containers comprising the steps of:
 a. introducing pressure fluid to an interior of a preform in a mold cavity to form a blow molded plastic container;   b. providing a sound detector assembly including a reflector having a substantially conic section cross-sectional shape and a sound detector;   c. acoustically sensing a defect sound with the sound detector assembly resulting from the pressure fluid escaping from the interior of the container; and   d. generating a control signal in response to the sensed defect sound.   
     
     
         2 . The method of  claim 1 , wherein the sound detector has a parabolic cross-sectional shape. 
     
     
         3 . The method of  claim 1 , wherein the sound detector has a hyperbolic cross-sectional shape. 
     
     
         4 . The method of  claim 1 , wherein the sound detector has an elliptical cross-sectional shape. 
     
     
         5 . The method of  claim 1 , wherein the sound detector has one of a substantially rectangular opening and a substantially circular opening. 
     
     
         6 . The method of  claim 5 , wherein the sound detector has a substantially rectangular opening formed from a pair of curvilinear walls joined together by a pair of rectilinear walls. 
     
     
         7 . The method of  claim 1 , wherein the sound detector includes a support extending between walls thereof. 
     
     
         8 . The method of  claim 7 , wherein the support forms an aperture adapted to receive the sound detector. 
     
     
         9 . The method of  claim 8 , wherein the aperture is disposed at one of a focus of the reflector and along a directrix of the reflector. 
     
     
         10 . The method of  claim 9 , wherein the aperture is disposed at the focus of the reflector and along the directrix of the reflector. 
     
     
         11 . The method of  claim 1 , wherein the step of producing a control signal includes amplifying the control signal. 
     
     
         12 . The method of  claim 1 , further including the step of rejecting the container having a hole therein. 
     
     
         13 . The method of  claim 12 , wherein the step of rejecting the container includes directing pressure fluid to reject the container having a hole therein. 
     
     
         14 . An apparatus for monitoring the production of blow molded plastic containers formed by introducing pressure fluid to an interior of a preform in a mold cavity comprising:
 a sound detector assembly adapted to be positioned adjacent a mold cavity during the introduction of pressure fluid to a preform in the mold cavity to form a container, said sound detector assembly including a sound detector and a reflector having a substantially conic section cross-sectional shape and being responsive to a defect sound of the pressure fluid escaping from the interior of the container for generating an output signal; and   means for generating a control signal in response to said output signal whereby a container rejecter receiving said control signal rejects the container.   
     
     
         15 . The apparatus of  claim 14 , wherein the reflector has one of a parabolic, hyperbolic, and elliptical cross-sectional shape. 
     
     
         16 . The apparatus of  claim 15 , wherein the reflector has a substantially rectangular opening formed from a pair of curvilinear walls joined together by a pair of rectilinear walls. 
     
     
         17 . The apparatus of  claim 14 , wherein the reflector includes a support extending between walls thereof, the support forming an aperture adapted to receive the sound detector. 
     
     
         18 . The apparatus of  claim 17 , wherein the aperture is disposed at the focus of the reflector and along the directrix of the reflector. 
     
     
         19 . An apparatus for monitoring the production of blow molded plastic containers formed by introducing pressure fluid to an interior of a preform in a mold cavity comprising:
 a sound detector assembly adapted to be positioned adjacent a mold cavity during the introduction of pressure fluid to a preform in the mold cavity to form a container, said sound detector assembly including a sound detector responsive to a defect sound of the pressure fluid escaping from the interior of the container for generating an output signal and a reflector having a substantially conic section cross-sectional shape and a support extending between walls thereof, the support forming an aperture adapted to receive the sound detector; and   means for generating a control signal in response to said output signal whereby a container rejecter receiving said control signal rejects the container.   
     
     
         20 . The apparatus of  claim 19 , wherein the aperture of the support is disposed at the focus of the reflector and along the directrix of the reflector.